The present invention relates generally to apparatus and methods for controlling hazardous dusts, mists, fumes, aerosols, and vapors, and more particularly to the use of a controlled pressure ventilation system to confine the work area while maintaining a flow of fresh air into the area.
The difficulty with controlling hazardous (including toxic) airborne dusts, mists, fumes, aerosols, and vapors is well-documented. This difficulty is further compounded when such materials must be controlled on an emergency basis as the result of a spill or a situation where uncontrolled dissemination of aerosolized contaminants would endanger lives or health. The removal of contaminated area air prevents the buildup of concentrations thereof in the work area. The neutral or positive pressure replacement of filtered air prevents the creation of uncontrolled negative pressures within the work area which may be destructive to the containment barriers, reduces the tendency of particles to become dislodged from their place of location, and provides a more comfortable environment for "clean-up" crews. Moreover, a neutral or positive pressure in the work area prevents the entrance of ambient contaminants which may interfere with the monitoring of the containment area.
In "Particulate Contamination Control Method And Filtration Device," U.S. Pat. No. 4,604,111 issued to Anthony Natale on Aug. 5, 1986, the inventor describes a negative pressure method and apparatus for protection from airborne asbestos and other particulate contamination including an enclosure with doorways and decontamination chambers having air intake therethrough with at least one filtration unit flow connected to the enclosure with a blower to pull air into the filtration unit and dispel the filtered air into the atmosphere. A high volume air flow intake is maintained resulting in a significant negative air pressure in the enclosure. Filtration devices are provided with multiple entrance ports to receive the discharge from separate vacuum cleaners as well as generating a large volume of air flow in the enclosure.
In "Differential Pressure Containment System" promotional literature distributed by The Brand Companies, 1420 Renaissance Drive, Park Ridge, Ill. 60068, the authors state that "While the `negative air` system remains useful, we have growing concerns for any approach which indiscriminately advocates the removal of large quantities of anything, including air, from that contaminated work area." They advocate the use of an air filtering device to exhaust the air in the region of contamination and so restrict the air entering the workplace that the pressure is reduced by a readable amount (to between 0.02 and 0.04 inches of water). It is stated that this pressure is above that at which plastic begins to float free from the floor and fall from the walls. Minimal amounts of air are released to the outside. As stated hereinabove, such a limitation in the flow of air into the contaminated region may produce uncomfortable working conditions for the individuals tasked with removing the source of contamination.
Accordingly, it is an object of the present invention to provide means for localizing a source of contamination while generating a significant flow of clean air into the region of contamination.
Another object of the present invention is to provide means for localizing a source of contamination while maintaining a desired pressure differential in the region thereof.
It is a further object of our invention to provide means for localizing a source of contamination while substantially preventing contaminant particles from being dislodged from their sites of location and entering the region of contamination.
Yet another object of our invention is to provide means for localizing a source of contamination while substantially preventing ambient materials from interfering with the measurement of the degree of contamination in the region thereof.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.